This invention relates to a process for the alkylation of an isoparaffin with an olefin acting agent. Additionally, the invention relates to a low acid alkylation process in which a novel catalyst is used to produce an alkylate having improved antiknock properties. Accordingly, the invention has particular utility in the production of high octane alkylate for use as a motor fuel blending component.
Alklation of isoparaffinic hydrocarbons, such as isobutane and isopentane, with olefinic hydrocarbons such as propylene, butylene and amylenes or with other olefin-acting agents such as C.sub.3 -C.sub.5 alkyl halides, etc., using mineral acids such as hydrogen fluoride is well known as a commercially important method for producing gasoline boiling range hydrocarbons. The C.sub.5 -C.sub.10 hydrocarbons typically produced in isoparaffin-olefin alkylation operations are termed "alkylate." Alkylate is particularly useful as a motor fuel blending stock. It possesses motor and research octane ratings high enough that it may be employed to improve overall octane ratings of available gasoline pools to provide motor fuels which comply with the requirements of modern automobile motors. High octane alkylate blending components are particularly important in producing motor fuels of sufficiently high octane when it is desired to avoid use of alkyl lead antiknock compounds in gasoline. A continuing goal in the art is to provide an economically attractive acid catalyzed alkylation process which provides an alkylate product having motor and research octane ratings which are higher than are attainable in conventional alkylation processes. This goal takes on special significance with the phaseout of alkyl lead antiknock compounds as blending agents for gasoline as mandated by government regulation.
In commercial isoparaffin-olefin alkylation operations using acid catalysts, generally, isobutane is the isoparaffin used and propylene, butylene and amylenes or a mixture of these olefins, are used as the olefin-acting agent. Typically the acid catalyst will comprise hydrogen fluoride. In conventional operations, the isoparaffin, olefin-acting agent and hydrogen fluoride catalyst are first contacted and thoroughly admixed in an alkylation reactor, forming a reaction mixture, or emulsion. After a relatively short time, the alkylation reaction is substantially complete and the reaction mixture is withdrawn from the alkylation reactor and is allowed to settle by gravity into immiscible hydrocarbon and catalyst phases in a settling vessel. The hydrogen fluoride catalyst phase thus separated is returned to the alkylation reactor for further catalytic use. The hydrocarbon phase separated in the settling operation is further processed, e.g., by fractionation, to recover an alkylate product and to separate unconsumed isoparaffin for recycle to the alkylation reactor. The recovered alkylate product may then be added to the motor fuel octane pool as a blending component. It is, therefore, desirable that the alkylate product has as high a research octane number as possible.